Liftoff! NASA Launches Twin Probes to Study Earth's Radiation Belts

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An unmanned rocket turned night into day early Thursday (Aug. 30)
as two heavily armored NASA spacecraft finally launched into
orbit to study Earth's harsh radiation belts after a week of
delays.

The twin
Radiation Belt Storm Probes mission launched at 4:05 a.m. EDT
(0805 GMT) today from Florida's Cape Canaveral Air Force Station,
lighting up the predawn sky as it soared into space atop an
unmanned United Launch Alliance Atlas 5 rocket. The liftoff had
been planned for Aug. 23, but it was pushed back two days due to
technical glitches, and then another five days to avoid foul
weather from Tropical Storm Isaac.

"It was a wonderful event, a very smooth countdown," NASA launch
manager Tim Dunn said after the launch, adding that the Atlas 5
gave NASA's newest science satellites "a great ride."

"We're all thrilled. Just excited as can be," Dunn added.

After a 60-day commissioning period on orbit, the new
radiation-tracking spacecraft will begin the science phase of
their two-year mission, which aims to help scientists understand
how Earth's two doughnut-shaped
Van Allen radiation belts affect our planet's space weather.

Such information could have considerable practical applications,
researchers said, since extreme
space weather can knock out satellites and disrupt GPS
signals, radio communications and power grids.

"RBSP will be able to predict the extremes and the dynamic
conditions of space weather," Mona Kessel, program scientist for
the $686 million mission at NASA headquarters in Washington,
D.C., told reporters in a prelaunch briefing on Aug. 20.
[ Launch
Photos: NASA's Radiation Probes Blast Off ]

Mysterious radiation belts

The twin solar-powered probes will ply the Van Allen belts, where
trillions of high-energy charged particles from the sun have been
trapped by Earth's magnetic field. These fast-moving particles
can damage satellites and potentially pose a threat to orbiting
astronauts.

To deal with this harsh radiation environment, critical
components on each RBSP spacecraft are shielded by 0.33 inches
(8.5 millimeters) of aluminum.

The inner Van Allen belt usually extends from the top of Earth's
atmosphere to about 4,000 miles up (6,437 kilometers), while the
outer one runs from around 8,000 to more than 26,000 miles above
our planet (12,874 to 41,842 km). The belts are dynamic, however,
and can
expand greatly during solar storms.

Though the two belts were discovered in 1958, they remain
mysterious today. For example, the belts sometimes react quite
differently to seemingly similar solar outbursts, for reasons
scientists don't yet understand.

The RBSP team hopes the twin probes can help researchers get to
the bottom of such puzzles.

"RBSP was designed to answer the questions of how these radiation
belts are responding," said mission deputy project scientist
Nicola Fox, of the Johns Hopkins University Applied Physics
Laboratory in Laurel, Md.

And launching two spacecraft rather than one is not redundant,
either, scientists said. The probes' observations will allow
researchers to determine whether differences in radiation levels
inside the belts reflect changes across space or time.

RBSP's measurements could also have more immediate benefits, they
added.

The probes' observations "will be delivered in near real time to
users all over the world, so that those users can use the space
weather data to protect sensitive ground-based as well as
space-based assets," said Michael Luther, deputy associate
administrator for programs for NASA's Science Mission
Directorate.